Radio receiving apparatus and the like



April 3, 1934. 1, wo 1,953,523

RADIO RECEIVING APPARATUS AND THE LIKE Filed April 9, 1932 HIS ATTOEIVE K Patented Apr. 3, 1934 lrving Wolff, Mcrchantvilie, N. J., assigncr to Radio Corporation of America, a corporation of Delaware Application April 9, 1932, Serial No. 604,152- l Claims. (Cl. 250-44) he present invention relates to radio receiving appalc-ltus and the like embodying sound producing :means a cabinet in which said sound .producinmeans is mounted along with 3 other portions the apparatus. More particularly, the present invention is in the nature or" an improvement over the invention disclosed in my U. S. patent Method and apparatus for j eliminating the effect oi? cabinet resonance, No. 19 1,901,383, died April 18, 1:930, and assigned to the Radio Corporation of America,

In the application referred to, it is pointed out that a diaphragm or vibratory member such as that provided by the cone of a loudspeaker disposed in a cabinet, develops a relatively high pressure region in the cabinet about the diaphragm or vibratory member, and that this pressure is increased substantially by the joint effects of the cabinet and the diaphragm when the latter vibrates at a frequency Within the natural resonant frequency range of the cabinet.

It is also shown that the acoustic effect of the cabinet, due to its natural resonant frequency, may be eliminated, the action being such that a certain part of the energy at the diaphragm is absorbed or disposed to prevent development of vibrations in the cabinet.

In accordance with the invention therein disclosed, undesirable acoustic action in sound producing apparatus, comprising a cabinet resonant within a given frequency range and a vibratory member associated with said cabinet, is avoided or eliminated by developing within the cabinet, during operation of the apparatus, within said frequency range, a relatively low pressure region Within said cabinet Where a relatively high pressure would otherwise develop, such for example, as in the space surrounding the vibratory member.

To this end, means are disposed in the cabinet and supported independently of and in spaced relation with respect to the associated diaphragm or vibratory member, said means providing a resonator or resonators tuned to resonate within the natural resonant frequency range of the cabinet, and to develop a relatively low pressure region in the cabinet where a 'elatively high pressure region wouid otherwise develop, such as in the vicinity of the vibratory diaphragm of the loud speaker or sound producing device. For this purpose the resonator or resonators are provided with openings adjacent to the vibratory member of the sound producing device. In certain instances a single resonator may be adequate,

the space Within the cabinet.

while in others a plurality of resonators may be necessary.

It is obvious that the resonators, as disclosed in the application, occupy a definite portion of If the cabinet dimension's are restricted, as is the tendency in modern receiver design, the resonators may interfere with proper positioning of the apparatus, such as the shielded receiver chassis, the power supply unit, and the loudspeaker.

Because of the fact that modern radio receiver cabinets are, preierabl of small dimensions and because or the fact that they are extremely sensitive and must be extremely selective, additional shielding must be provided, preferably in the form of a metallic housing, for the receiver chassis. This shield materially increases the bull; oi the receiver chassis and necessarily occupies a greater cabinet space than would the simpler unshielded chassis of earlier radio receiv- $5 ing apparatus.

Accordingly, it is an object of the invention to provide means, for eliminating receiver cabinet resonance, that shall occupy minimum space.

It is a further object of the invention to provide tuned resonator means of the type described, that may be tuned to the most enicient point after assembly of the apparatus in a cabinet.

The foregoing objects and other objects appurtenant thereto are preferably accomplished by utilizing a portion of the receiver or receiving apparatus itself, as a resonator. More specifically, a relatively heavy metallic shield is provided as an enclosing means for the radio receiver chassis, whereby the chassis is completely shielded and the walls of the shield, being or" relatively heavy metal, provide a chamber which is utilized as a resonance chamber. ihe shield is so related to the loud speaker or sound producing device within the cabinet that openings in the shield may be provided adjacent to the sound producing device. The shield is, therefore, utilized as a resonance chamber.

As a preferred embodiment of my invention there are provided a plurality of openings in one wall or the resonator or shield, which openings may or may not be adjustable to vary the area of the communication channel between the interior or" the shield and the interior of the cabinet.

. In a preferred embodiment of th invention the power supply unit and the loud speaker are located in the lower portion or bottom of the receiver cabinet, and the receiver chassis enclosed in a rigid metallic shield, is mounted directly above the loud speake The shield is then reso- 310 application.

nated by providing suitable openings in the bottom of the shield adjacent to the loud speaker. For tuning such resonator after assembly, the openings may be made adjustable.

The invention will, however, be better understood from the following description when taken in connection with the accompanying drawing, and its scope Will be pointed out in the appended claims.

In the drawing, Figure 1 is a cross-seotional view in elevation, of a radio receiving apparatus embodying the invention;

Fig. 2 is a bottom view of a portion of the apparatus shown in Fig. 1, looking in the direction of arrows on line 2-2, illustrating a feature thereof in greater detail; and

Fig. 3 is a detailed view of a portion of the apparatus shown in Fig. 1, illustrating a detail modification thereof.

Referring to Figs. 1 and 2, 5 is a receiver cabinet of the usual conventional design, having an apparatus panel 6 and a loud speaker grille 7 therein at the front, and an open back 8.

Within the cabinet is mounted a radio receiving apparatus including, at the bottom, a power supply unit 9 and a sound producing device or loud speaker 10 having a vibratory element or diaphragm indicated at 11.

Directly above the loud speaker or sound producing unit is mounted a receiver chassis 12, enclosed in a rigid metallic shield 13 forming a complete enclosure for the chassis. The shield is provided with a removable back 14 whereby access may be had to the tubes and other apparatus in the receiver chassis. in the back is secured to the remainder of the shield to tig tly enclose the receiver chassis.

The shield 13 may be electro-static or electromagnetic in character, as a shield means for the apparatus, but in any event is of metal of sufficient gauge to provide rigid substantially nonvibratory walls for a chamber 15, within it.

It will be noted that, from the position of the apparatus as arranged in the cabinet, the interior of the shield 13 or the chamber 15 may be placed in direct communication with the interior of the cabinet by simply providing openings in the bottom of the shield as indicated at 16. While this is a present preferred arrangement, it is obvious that communication between the chamber and the region adjacent to the loud speaker or sound producing device may be provided in a similar manner with other apparatus, for example in receivers having the sound producing device or loud speaker mounted directly above the re ceiver chassis, the communicating opening or openings being provided, preferably, in the wall of the chamber adjacent to the loud speaker.

It will be seen that, by providing a rigid shield about the receiver chassis per se, as is desirable and necessary for electrical shielding purposes, and locating the loud speaker or sound producing device adjacent to one wall thereof, the shield or chamber therein may be utilized as a resonator for correcting for acoustical resonance within the cabinet.

In the present example, as indicated in Fig. 2, a plurality of openings are provided to effect the desired area of the communication channel with the chamber 15. The area necessary to effect 2.

neutralization of the tendency of the cabinet to resonate within the audio frequency range, may and does vary with different types of cabinets and with different types of apparatus therein, and even with substantially equal and the same designs, may vary slightly one with respect to the other.

Accordingly, it is desirable to provide means for adjusting the area of the opening or openings providing communication between the resonance chamber and the interior of the cabinet. To this end, by way of example, the openings 16 in the shield wall of Figs. 1 and 2 may be arranged as indicated at 17, Fig. 3, to lie in equal spaced relation to each other in a circle about a common center 18 in a wall 19 of the shield 13. A circular, rotary cover plate 20 having similar spaced openings 21 therein adapted to permit the openings 21 to register with the first named openings when the cover plate is rotated. By this arrangement the openings 17 may be fully opened or partially or completely covered to provide a desired area of communication between the interior of the cabinet and the chamber. Suitable means, such as a wing lock nut 22, is provided for securing the cover plate 20 in adjusted position. Obviously, any other suitable means for adjusting the position of the area of the communication channel between the resonator chamber and the interior of the cabinet, may be provided, al-

though the means shown is at present preferred.

From the foregoing description it will be seen that, in accordance with the invention, as a means for eliminating receiver cabinet resonance or the resonance of any cabinet which may contain a sound producing device having a vibratory member and a shielded apparatus, the apparatus may be provided with an enclosing shield and may be placed in communication with the region surrounding the sound producing device, by suitable openings to utilize the shield as a resonator device for correcting for cabinet resonance. As a present preferred embodiment, an opening or a plurality of openings which may or may not be adjustable, are provided in a wall of a rigid metallic shield enclosing a radio receiver chassis or the like and the shield is utilized as a resonance chamber and as a shield simultaneously. The construction of the apparatus is thereby simplified the space required is greatly reduced.

While the invention has been illustrated and described in its specific application to a radio receiving apparatus, it is obvious that it is not limited thereto, but may be applied to any electrical apparatus embodying elements requiring j electro-static shielding and a sound producing device having a vibratory element, all mounted in a cabinet subject to cabinet resonance within the operating range of sound frequencies of the sound producing device.

I claim as my invention:

1. In combination, a cabinet, electrical apparatus within the cabinet, a sound producing device having a diaphragm associated with the cabinet whereby said cabinet provides a sound pro jecting cafile member therefor, and audible frequency resonator means including an attenuator chamber having rigid metallic walls providing a container and electrical shield for said electrical apparatus, and one of said metallic walls having 1.

at least one opening communicating directly with the interior of the cabinet adjacent to the diaphragm of the sound producing device.

2. In combination, a cabinet, electrical apparatus within the cabinet, a sound producing de 1 i vice associated with said cabinet, unitary metallic container means for shielding the electrical apparatus against stray electric fields and for attenuating sound waves tending to cause cabinet resonance within the frequency range of opera tion of the sound producing device, said container means being associated with the sound producing device and having walls providing a chamber communicating with the exterior thereof only through a wall adjacent to said device, and means for varying the area of communication through said wall, whereby said container is acoustically tunable.

3. In combination, a cabinet, electrical apparatus within the cabinet, 2. sound producing device associated With said cabinet, and unitary metallic container means for shielding the electrical apparatus against stray electric fields and for attenuating sound waves tending to cause cabinet resonance within the frequency range of operation of the sound producing device, said unitary metallic container means being provided with at least one opening in a wall thereof adjacent to the sound producing device.

4. The combination with a loud speaker diaphragm and a cabinet associated therewith as a balile and enclosure means therefor, of an electrical shield means associated with said cabinet and loud speaker and including a metallic walled apparatus container providing a resonator chainber in communication With the interior of the cabinet adjacent to the diaphragm.

5. The combination with an electrical apparatus, a sound producing device having a vibratory element, and a cabinet for said apparatus ant. sound producing device, of electrical shield means for said apparatus including a metallic container having rigid walls, and said container having at least one opening in one of said walls adjacent to the vibratory element of the sound producing device, and being acoustically resonant to attenuate sound waves within a predetermined range of sound frequencies.

6. In combination, a cabinet, electrical apparatus within the cabinet, a sound producing device associated with said cabinet and having a vibratory element located therein, and unitary means for shielding the electrical apparatus against stray electric fields and for substantially eliminating cabinet resonance resulting from operation of said sound producing device, said last named means including a metallic container for the apparatus providing a resonance chamber having rigid walls one of which is located adjacent to said vibratory member of the sound producing device, and means providing adjustable openings in said last named wall for adjusting the acoustical resonance of said metallic container as a resonator to attenuate sound waves generated within the cabinet.

'7. In combination, a cabinet, electrical apparatus within the cabinet, a sound producing device associated with said cabinet and having a vibratory element located therein, and unitary means for shielding the electrical apparatus against stray electric fields and for substantially eliminating cabmet resonance resulting from operation of said sound producing device, said last named means including a metallic container for the apparatus providing a resonance chamber having rigid walls one of which is located adjacent to said vibratory member of the sound producing device, and having an opening providing a sound conducting channel between the interior of the chamber and the interior of the cabinet adjacent to the vibratory element.

8. In apparatus of the character described, a cabinet normally resonant within a given frequency range, a vibratory sound producing phragm member associated with said cabinet whereby the latter provides a sound projecting baffie for said vibratory member, electrical apparatus mounted in said cabinet, a metallic casing for said apparatus providing an electrical shield means therefor ans a sound wave attenuating chamber, and means providing a sound conducting opening through a wall of the chamber between the interior of chamber and the interior of the cabinet adjacent to the vibratory diaphragm member.

9. The combination wi h a loud speaker diaphragm and a cabinet associated therewith as a baille and enclosure means therefor, of an electrical shield means associated with said cabinet and loud speaker and including a metallic walled apparatus container providing a resonator chamber in communication with the interior of the cabinet adjacent to the diaphragm, and electrical apparatus associated with the cabinet located in said container whereby it is shielded electrically and space within the cabinet is conserved.

10. In apparatus of the character described, a cabinet normally resonant within a given frequency range, a vibratory sound producing diaphragm member associated with said cabinet whereby the latter provides a sound projecting baiile for said vibratory member, electrical apparatus mounted in said cabinet, a metallic casing for said apparatus providing an electrical shield means therefor and a sound wave attenuating chamber, said casing having at least one opening leading into the interior thereof and to said chamber and disposed adjacent to the diaphragm member, said opening providing a sound conducting channel, and means for varying the area of said channel.

11. In apparatus of the character described, a cabinet normally resonant within a given sound frequency range, a vibratory member associated with said cabinet, means for imparting vibratory movement to said member within said range, means disposed within said cabinet and providing a resonator chamber operable to compensate for acoustic action of said cabinet with respect to said member during vibration of the latter within said frequency range, apparatus disposed within said chamber and forming part of said firstnamed means, the walls of the resonator chamber being of metal to form an electrical shield for said appartus, and the interior of said chamber being in communication with a sound pressure region adjacent to the vibratory member within the cabinet.

12. In a sound producing apparatus, the combination of a sound producing device having a movable diaphragm, a cabinet providing a sound directing baflie means for the diaphragm, means for providing a metallic-walled sound attenuating resonator chamber in the cabinet, one of the walls of said chamber being located adjacent to said diaphragm and having at least one opening providing a sound communicating channel between the interior of the chamber and the interior of the cabinet adjacent to said diaphragm, electrical apparatus associated with the cabinet located in said chamber whereby the space in the cabinet therefor is conserved and whereby said apparatus is electrically shielded, said chamher being of such size and the area of the sound communicating channel I being such that, the

chamber is resonant with the pparatus therein "relatively large area of the diaphragm being enclosed only by the cabinet, of 'a resonator chamber positioned in said cabinet adjacent to said area of "the diaphragm of said sound producing device and having communication'through openings in one of the walls of said chamberdirectly with the region of the interioriof the cabinet im-. mediately adjacent to said area of the diaphragm, said resonator chamber having substantially rigid metallic walls, electrical apparatus mounted in said chamber whereby the walls of said chamber provide an electricalishield therefor, and means associated with said openings for acoustically tuning said chamber to resonate withina predetermined sound frequency range.

14. A radioreceiver including in combination,

a radiloreceiving apparatus, a loud speaker having an exposed diaphragm, a cabinet providing an I enclosure and mounting means for theapparatus andtheloudspeaker and a bafile means for the latter, a metallic rigid-walled casing enclosing. the.

apparatus as an electrical shield therefor, said casing providing an acoustical resonator chamber for attenuating sounds within a pr determined range of sound frequencies and communicating with a region in the cabinet adjacentto the loud speaker diaphragm.

l5. Arad io receiver including in combination,

a cabinet, a loud speaker having adiaphragm.

associated with the cabinet whereby the latter operates as a battle meanstherefor, radio receiving apparatusassocialbed with the loudspeaker in the cabinet, and means for attenuating sound waves in said cabinet within a predetermined sound frequency range, said meanscomprising a metallic-walled resonator chamber communicating with a region inthe cabinet adjacent to the diaphragm, and said radio receiving apparatus 7 being locatedin said chamber whereby it is electrically shielded by the walls thereof.

IRVING WOLFF. 

